Stormwater runoff cisterns are roof water management devices that provide retention storage volume in above or underground storage tanks. They are typically used to supplement the water supply for landscape irrigation. Cisterns are substantially larger than rain barrels, with some underground cisterns having the capacity of 10,000 gallons or more. They are also typically equipped with an electric pump to facilitate pressurized distribution to an automated landscape irrigation system. Cisterns are constructed of durable material, such as concrete, plastic, polyethylene, or metal.